The present invention relates to an apparatus for providing heat to wafers and more particularly to an apparatus for rapid thermal processing of wafers.
Heat treatment apparatuses are used in a variety of industries including the manufacture of semiconductor devices. These heat treatment apparatuses can be used for several different fabrication processes such as thermal annealing, thermal cleaning, thermal chemical vapor deposition, thermal oxidation and thermal nitridation. These treatments often require that the temperature of a wafer be elevated to as high as 350xc2x0 C.-1300xc2x0 C. before and during the treatment. Further, these treatments often require that one or more fluids be delivered to the wafer.
There are several design challenges to meeting the thermal requirements of heat treatment apparatuses. For instance, it is often desirable to quickly ramp up and/or down the temperature of a wafer to be treated. During these rapid temperature changes the temperature uniformity of the wafer should be sufficient to prevent damage to the wafer. Wafers often cannot tolerate even small temperature differentials during high temperature processing. For instance, a temperature difference above 1xc2x0-2xc2x0 C./cm at 1200xc2x0 C. can cause enough stress to produce slip in the silicon crystal of certain wafers. The resulting slip planes will destroy any devices through which they pass.
Delivery of fluid to the wafer can also present design challenges. For instance, the exposure of the wafer to the fluid should be uniform across the wafer to avoid uneven treatment results. Further, fluids within the heat treatment apparatus must often be rapidly evacuated from the heat treatment apparatus. Another challenge derived from fluid delivery is the replacement of fluids within the heating chamber with other fluids. This exchange of fluids must often occur with minimal interaction between the original and replacement fluids.
The invention relates to a heat treatment apparatus. The apparatus includes a heating chamber having a heat source. A cooling chamber is positioned adjacent to the heating chamber and includes a cooling source. A wafer holder is configured to move between the cooling chamber and the heating chamber through a passageway. One or more shutters defines the size of the passageway and are movable between an open position where the wafer holder can pass through the passageway and an obstructing position which defines a passageway which is smaller than the passageway defined when the shutter is in the open position. Of particular advantage, the shutters promote thermal isolation and chemical isolation of the heating chamber and cooling chamber.
Another embodiment of the apparatus includes a heating chamber positioned adjacent to a cooling chamber. A wafer holder is configured to be positioned in the cooling chamber at a loading position where the wafer can be removed from the wafer holder. The wafer holder is movable between the cooling chamber and the heating chamber. A cooling source such as a cooling plate is positioned in the cooling chamber so as to be positioned beneath the wafer holder when the wafer holder is positioned in the loading position.
Another embodiment of the apparatus includes a heating chamber with a closed upper end. A plurality of heating elements are positioned above the closed upper end of the heating chamber. The upper end of the heating chamber includes a heating plate which is configured to receive thermal energy from the heating elements and distribute the thermal energy in a substantially uniform manner over a surface of the heating plate which is positioned within the heating chamber. The heating plate includes a plurality of fluid ports which are configured to be coupled with a fluid source. A wafer holder is configured to be positioned in the heating chamber such that a wafer held by the wafer holder receives fluid delivered into the heating chamber through the fluid ports.
Another embodiment of the apparatus includes a cooling chamber positioned adjacent to a heating chamber. A wafer holder is coupled with at least one shaft which is driven so as to move the wafer holder between the cooling chamber and the heating chamber through a passageway. Two or more shutters are positioned adjacent to the passageway and are movable within a horizontal plane so as to define the size of the passageway. The two or more shutters are movable to an obstructing position where the two or more shutters encompass the at least one shaft coupled with the wafer holder.
The invention also relates to a heat treatment apparatus having a heating chamber and one or more fluid inlet ports for delivery of a fluid into the heating chamber. A member extends into the heating chamber from a side of the heating chamber at a height below a height of the fluid inlet port. The member has an edge with a shape which is complementary to the perimeter of a portion of the wafer to be treated in the apparatus. A wafer holder is movable within the heating chamber and can move the wafer adjacent to the member to define a fluid flow region within the heating chamber.
Another embodiment of a heat treatment apparatus having a heating chamber and one or more fluid inlet ports for delivery of a fluid into the heating chamber includes a flow distribution chamber which distributes a flow of fluid from the one or more fluid inlet ports. The flow distribution chamber is positioned such that fluid from the fluid inlet port enters the heating chamber through the flow distribution chamber.
The apparatus can also include a fluid exhaust port for withdrawing fluid from the heating chamber and a second flow distribution chamber for distributing a flow of fluid from the heating chamber to the fluid exhaust port. The second flow distribution chamber is positioned such that fluid from the heating chamber enters the fluid exhaust port through the flow distribution chamber.
A flow distribution chamber associated with a fluid inlet port can include a flow distribution member positioned such that fluid from the fluid inlet port enters the heating chamber through the flow distribution chamber. Similarly, a flow distribution chamber associated with a fluid exhaust port can include a flow distribution member positioned such that fluid from the heating chamber enters the fluid exhaust port through the flow distribution chamber.
The invention also relates to a method for rapid thermal processing of a wafer. The method includes providing a heating chamber having a heating plate and heating the heating plate. The method also includes positioning a wafer in a wafer holder and moving the wafer holder toward the heating plate until the wafer is positioned close enough to the heat source for heat to be conducted from the heating plate to the wafer.
The method can also include backing the wafer holder away from the heating plate after a target condition has been achieved at the wafer and delivering a fluid into the heating chamber from above the wafer holder.
In another aspect, the present invention provides a wafer holder and heat treatment apparatus configured to promote more uniform heating of the wafer.
In yet another aspect, the heating treatment apparatus provides improved containment of the gases within the heating chamber by establishing a pressure differential between the heating and cooling chambers and flowing a purge gas.